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Canadian Plavix Decision: Implications For Pharmaceuticals And Biotech Inventions

Issue 2008/13 | Tuesday, December 23rd, 2008

By Adrian Zahl, RIDOUT & MAYBEE LLP, Canada

In a recent decision of particular significance for pharmaceutical and biotech inventors, the Supreme Court of Canada upheld “selection” patents and signaled a shift in Canada’s approach to obviousness and anticipation (Apotex Inc. v. Sanofi-Synthelabo Canada et al (2008 SCC 61)). The decision brings Canada into closer alignment with the United States and the UK.

The case involved a challenge to Sanofi’s patent for Plavix, a blood clot drug. Sanofi had initially obtained a patent for a broad class of compounds, which included an example directed to a “racemic mixture” of two optical isomers, or enantiomers. This patent expired in 2003. After filing the first application, Sanofi separated the two isomers and determined that one of these was highly effective as a drug, while the other was not only ineffective but also toxic. They described and claimed this isomer, and its bi-sulfate salt, in a subsequent patent, 1,336,777. Apotex challenged the ‘777 patent in order to market a generic version of Plavix, alleging anticipation, double patenting, and obviousness. The court’s ruling on anticipation and obviousness are of particular interest.

The court initially outlined the criteria for patenting a “selection” from a previously-disclosed class of substances:

there must exist a substantial advantage or disadvantage to be avoided in the selection (which can consist of a sub-class or individual member of the original class)

essentially all of the selected members must possess this advantage

the advantage must be peculiar to the selected group, although a small portion of the non-selected class may subsequently be shown to also possess this advantage.

The prior disclosure cannot have anticipated the invention. Anticipation occurs if the special properties of the selected members were previously disclosed, and the prior disclosure also “enabled” production of the selected members. The second requirement means that the skilled reader must have been provided with sufficient information within the prior disclosure to make and use the selection. Experimentation is permitted for this purpose, so long as this is routine and not “undue.” The degree of permitted experimentation depends on whether it is common to carry out experiments in the relevant field. Pharmaceutical and biotech inventions may thus have to meet a somewhat higher threshold to be considered patentable.

The court’s ruling on anticipation has broad implications for patents in the chemical and biological arts. For example, prior art which merely disclosed a chemical formula without any teaching of how it could be prepared might not have previously constituted an “enabling disclosure.” Now, such prior art could anticipate an invention if non-undue experimentation would teach the skilled person how to make such compounds.

The ruling also has implications for obviousness. Traditionally, the Canadian test for obviousness involves the rigid application of a simple question, namely whether the skilled person “without a scintilla of inventiveness” would have been led directly and without difficulty to the solution taught by the invention. Typically, it is difficult to invalidate a patent on this basis. The court addressed a difficulty with this test when applied to experiment-driven fields such as chemistry or biotech, in that it can reward inventions arising from purely routine experiments, if one can show that at least some trial and error was involved for which the results were unpredictable. The court stated that an invention can be obvious if the prior art suggested that it was “worth a try” to make the invention, especially if the invention is in a field in which advances usually achieved by experimentation. Considerations to be applied are:

Was it self-evident that what is being tried ought to work, and were there a finite number of predictable solutions?

Were routine trials or prolonged experimentation required to achieve the invention?

Was there a motive to find the solution that the patent addresses?

In this case, the court observed that it was known in principle that the properties of a racemate and its individual isomers can sometimes differ. However, this was not self-evident in this case, nor was it evident which of the separated isomers would be superior. There also existed several possible ways to separate the isomers, and the selected method was not self-evident. The inventors’ own efforts were evidence of non-obviousness: Sanofi had expended considerable effort developing the original racemate as a drug before finding that the separated isomer was superior, at which point it abandoned its earlier efforts. The inventors spent some 6 months separating and testing the isomers.

The Sanofi decision may, paradoxically, make it more difficult to obtain selection patents in the future. The Plavix patent at issue was filed in 1988. However, more recently-filed patents may become a victim of technical advances in medicinal chemistry. Separation and testing of optically active compounds has become easier, and it is now routine to test individual enantiomers (the isomers of optically active compounds) to determine which is the more effective. Courts may find that newer selection patents were based on routine trial and error and are obvious.

The Sanofi decision, coupled with recent Federal Court jurisprudence, signals a shift away from the traditional purely objective test of obviousness. The traditional test may now longer apply to experiment-driven fields, where research is often advanced by trial and error rather than by flashes of inspiration. In such fields, inventors may be required to show sufficient “sweat of the brow” to merit a patent.

Previously, Canada represented something of an outlier amongst the major jurisdictions in its relatively low standard of obviousness. However, the new multi-factorial test raises the bar in that it permits a court or patent examiner, if inclined, to select from an arsenal of factors to find an invention obvious. Canada is now closer aligned with the U.S. and the UK (and to an extent, the EPO) in this regard.

It is interesting to contrast the use of evidence for determining obviousness, with construction of a patent. Inventors may now introduce evidence of their own r & d efforts when fending off a charge of obviousness. However, it is not permissible in Canada to introduce the patent file history or other “intrinsic” evidence when construing the patent for infringement purposes.

This decision reinforces the importance for inventors to keep clear records of their research, including all failed experiments, and also take other steps to establish a strong evidentiary position in advance that the invention was not worth a try based upon the prior art, given their own efforts in developing the invention. The high standard of obviousness also makes it important to exercise considerable care when preparing a patent application.

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